1. Field of the invention
The present invention relates to the manufacture of structural members and, more particularly, relates to an apparatus and method for forming a contoured structural member.
2. Description of Related Art
Composite members are commonly used in applications, such as aircraft and other vehicles, where light weight and high strength are desired or required. Often the composite members must be formed in a contoured configuration according to the particular application for the member. Complex contoured composite members are typically configured in a desired configuration while the composite material is in a “green” or uncured condition and then cured while supported in the desired configuration. One conventional method for forming such contoured composite members is by manually laying the composite materials onto a mandrel or other tool defining a male pattern corresponding to the desired configuration. For example, the composite material can be disposed as pre-impregnated composite fiber plies (“prepregs”) such as epoxy impregnated carbon fiber laminates. The plies are laid by hand onto the mandrel, and cured on the mandrel to form the member, typically using heat and/or pressure. Alternatively, the composite material can be disposed as dry fabric plies (“dry fabric”), and a bonding material can be added separately. In either case, the resulting structural member can be formed in a variety of desired shapes. However, such a manual layup process is time-consuming. Further, a separate mandrel must typically be provided for forming each particular configuration of composite member.
According to another conventional method for manufacturing composite members, known as drape forming, a flat sheet-like laminate charge or blank of composite material is formed against a mandrel. In particular, the charge is heated and forced around the male mandrel using a vacuum bag. Drape forming has been used successfully to form composite parts where the parts being formed have only a few prepreg plies. However, for thick laminates and complex shapes such as composite members defining C-, I-, or L-shaped beams, long flange lengths, contours along their length, variable thicknesses, joggles (or changes in direction), or offsets, vacuum bag drape forming can result in wrinkling of the plies.
U.S. Patent Application Publication No. 2004/0043196, titled “Forming Method for Composites,” published Mar. 4, 2004, which is assigned to the assignee of the present application, describes a system and method for forming composite materials and reducing buckling of the fibers of the composite material. In particular, a composite charge can be formed over a mandrel using bladders and heater plates. U.S. Patent Application Publication No. 2004/0041304, titled “Composite Spar Drape Forming Machine,” published Mar. 4, 2004, which is also assigned to the assignee of the present application, also describes a machine and method for forming composite materials about a mandrel. Both of U.S. Patent Application Publication Nos. 2004/0043196 and 2004/0041304 are incorporated by reference in their entirety.
While the foregoing devices and methods are useful for forming composite members, there exists a continued need for an improved apparatus and method for forming composite members. The method should be capable of producing composite members that define various contours, including contours including variations in thickness, curves, angles, flanges, and the like.